1. Field of the Invention
This invention relates to an automatic film wind up device, and more particularly to an automatic film wind up device which automatically winds up a film in a camera frame by frame using an electric motor.
2. Description of the Prior Art
Automatic film wind up devices which use an electric motor to drive a film wind up shaft to wind up a film in a camera have well been known in the art. The automatic film wind up devices generally use a drive disc connected to a motor, a driven dics connected to a film wind up shaft, and a clutch means to selectively transmit the rotation of the drive disc to the driven disc in synchronization with the feeding of the film. When the clutch is operated to disconnect the driven disc from the drive disc, the electric motor should be stopped. In order to stop the motor in synchronization with the feeding of the film, there has been used a mechanical detecting means which comprises cam means for moving one of the discs in the direction of the axis thereof and means for detecting the axial movement of the disc.
The mechanical detecting means employed in the conventional automatic film wind up devices is, however, disadvantageous in that the structure thereof is complicated and accordingly the manufacturing cost thereof is high and the device is apt to malfunction.